Comparative analysis of isonicotinic acid, l-ascorbic acid and calcium chloride on the induction of innate immunity and secondary metabolite production in Catharanthus roseus (L.) G. Don for management of biotic and oxidative stress

Abstract

Catharanthus roseus (L.) G. Don is an ornamental and pharmacologically important plant. It contains large amount of indole alkaloids having pharmaceutical activities. Production of vinblastine and vincristine, two important anti-cancerous secondary metabolites of C. roseus, are very less and hampered due to pathogen invasion. To overcome this problem here attempt has been made to boost innate immunity and secondary metabolite production in C. roseus by foliar application of three eco-friendly elicitors viz. Calcium chloride (CaCl2), l-Ascorbic acid (L-AA) and Isonicotinic acid (INA), each at two different concentrations. Augmentation of immune responses was observed in terms of increased production of defense related enzymes like PPO (polyphenol oxidase), PO (peroxidase), PAL (phenylalanine ammonia lyase assay), and β-1,3 glucanase; defense related compound production (total flavonoid and phenol content) and antioxidant enzyme activity (ascorbate peroxidase, APX and catalase, CAT) in C. roseus plant. Increased defense responses were noted in INA (1.25 mM), l-AA (5 mM) and CaCl2 (0.5 %) treated plants compared to control. Same concentrations of elicitors were also found effective in the induction of vinblastine and vincristine production which was detected by both qualitative (using dragendroff reagent) and quantitative methods using LC-MS (Liquid Chromatography-Mass Spectrometry). During this study, nitric oxide (NO) production was also found increased in elicitor treated plants and indicating its signaling role. Finally, challenge inoculation with Alternaria alternata showed significantly reduced disease incidence in elicitor treated plants which indicates their potentiality to combat against this pathogen.